<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script>
        /*
            按左键，往左移
            按右键，往右移
        */
        window.onload = function () {
            //为document绑定一个按下事件
            document.onkeydown = function (event) {
                event = event || window.event;
                //速度
                var speed=10;
                if(event.ctrlKey){
                    speed=50;
                }
                /*
                    37 左 
                    38 上
                    39 右
                    40 下
                */
                switch (event.keyCode) {
                    case 37:
                        box1.style.left = box1.offsetLeft - speed + "px";
                        break;
                    case 39:
                        box1.style.left = box1.offsetLeft + speed + "px";
                        break;
                    case 38:
                        box1.style.top = box1.offsetTop - speed + "px";
                        break;
                    case 40:
                        box1.style.top = box1.offsetTop + speed + "px";
                        break;
                    default:
                        break;
                }
            };
        };
    </script>
    <style>
        #box1 {
            width: 100px;
            height: 100px;
            background-color: red;
            position: absolute;
        }
    </style>
</head>

<body>
    <div id="box1"></div>
</body>

</html>